Electrical charging device

ABSTRACT

Corona discharge apparatus incorporating an electrode assembly comprising needle electrode pluralities providing corona discharge at opposite sides of a longitudinal passage in the apparatus through which a chargeable member is moved. Electrodes are spaced particularly in lateral and longitudinal manner for providing a uniform electrical charge on the chargeable member.

[ 1 July 4, 1972 [54] ELECTRICAL CHARGING DEVICE [72] Inventors: WilhelmJosef Knechtel, Rodheim; Detlef Schafler, Wetzlar, both of Germany 173Assignee: Canon Kabushiki Kaisha, Tokyo, Japan [22] Filed: July 13,1970

[21] Appl.No.: 54,334

[30] Foreign Application Priority Data 2,934,650 4/1960 De Witt..250/49.5 3,146,385 8/1964 Carlson ..250/49.5

Primary ExaminerJames Lawrence Assistant Examiner-C. E. ChurchAttorney-Watson, Leavenworth and Kelton ABSTRACT Corona dischargeapparatus incorporating an electrode assembly comprising needleelectrode pluralities providing corona discharge at opposite sides of alongitudinal passage in July 16, 1969 Germany ..P 19 36 168.3 theapparatus through which a chargeable member is moved. Electrodes arespaced particularly in lateral and longitudinal [52] U.S. CL.....250/49.5 ZC, 250/495 GC mann r f r pr vi ing a uniform electricalcharge on the [51] Int. Cl. ..G03g 15/00 h rgeable member. [58] Field ofSearch ..250/49.5 ZC, 49.5 TC

[56] References Cited 8 Claims, 5 Drawing Figures 2 UNlTl IDSflATESPATENTS 3,483,374 12/1969 Erben ..250/49.5

C C 2 C 3 C 4 D1 D 2 D 3 D4 BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to a corona discharger for applyingelectric charge to photosensitive paper, foil or like material, and moreparticularly to a corona discharger for use in photocopying apparatus.

2. Description of the Prior Art To electrically charge paper or foil,use is usually made of a wire electrode stretched transversely of thepath of movement of the paper. The wire electrode applies electriccharge to the moving paper by corona discharge.

In high speed photocopying apparatus wherein paper moves very quicklythrough the apparatus and accordingly moves very quickly below thecorona discharge, it has been found that electric charge is notsufficiently applied to the paper to provide excellent copy.

Therefore, it has already been proposed to replace the wire electrode bya needle electrode. In this case, the needle electrodes have their tipends juxtaposed with the paper to apply electric charge-thereto. Thisarrangement is still insufficient, because stripes of electric chargeare formed longitudinally of the fast moving paper and they clearlyappear in the resulting copy. This is not remedied even if a pluralityof needle electrodes are disposed one after another.

SUMMARY OF THE INVENTION The object of the present invention is to forma corona discharge which can provide sufficiently great and especiallyuniform distribution of electric charge even on fast moving paper.

Such object of the present invention can be achieved by providing anumber of needle electrodes, each having a voltage applied thereto, onboth sides of the path of movement of the paper in such a manner thateach needle electrode on one side is directed toward a gap betweenneedle electrodes on the other side and that none of the needleelectrodes on either side lies behind any other needle electrode asviewed in the direction of movement of the paper.

It has been found effective to provide at least two rows of needleelectrodes on each side of the path of movement of the paper in such amanner that the needle electrodes in one row on each side are spacedtransversely of the direction of movement of the paper with respect tothe needle electrodes in the other row on that side and that all theneedle electrodes on one side of the path of paper are directed towardgaps between the needle electrodes on the other side of the path ofmovement ofthe paper.

In another form of the present invention, the needle electrodes on bothsides of the path of paper are disposed in rows spaced transversely ofthe direction of movement of the paper.

The rows of needle electrodes on both sides of the path of paper mayconveniently be opposed to each other.

It has been found suitable that needle electrodes are disposed in tworows on each side of the path of movement of the paper in such a mannerthat the needle electrodes in one row are directed toward gaps withrespect to the needle electrodes in the other row.

With such an arrangement, it has been found that sufficiently great andsufficiently uniform electric charge can be distributed on the surfaceof the paper.

The last-named embodiment shows that a relatively small number of needleelectrodes can achieve the object of the present invention.

The invention will be described by way of example with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of anarrangement according to the present invention.

FIG. 2 is a cross-sectional view taken along plane lI-Il of FIG. 1.

FIG. 3 is a cross-sectional view taken along plane III-Ill of FIG. 1.

FIG. 4 is a schematic view taken in the direction of arrow IV in FIG. 1and showing the arrangement of the needle electrodes.

FIG. 5 shows a modified arrangement of the needle electrodes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 4,paper 1 passes between needle electrodes, each comprising an elongatedbody tapering to a corona discharge point. The needle electrodes, towhich a voltage is applied, emit electric charge onto the surface of thepaper. In FIG. 1, there are provided four rows of needle electrodesA,B,C,D. Corona discharge points P are thereby provided, as shown, e.g.,by the reference letters PA. The discharge points PA and PC ofelectrodes A and C are disposed in a common plane (III-lll) laterallytransverse to the paper passage. The discharge points PB and PD ofelectrodes B and D are disposed in a common plane (II-II) longitudinallyspaced from the plane IlIlII and also laterally transverse to the paperpassage. The respective rows comprise a plurality of needle electrodesAl-A4, Bl-B4, C1-C4 and Dl-D4 arranged in succession so as to occupy theentire width of the paper.

It is seen in FIG. 2 that needle electrodes C1-C4 are opposed to Dl-D4in such a manner that each needle electrode in one row is directedtoward a gap between the needle electrodes in the opposite row.

FIG. 3 shows four rows of needle electrodes A, B, C and D. The needleelectrodes in rows A and B are shown in cross section. It will be seenthat the needle electrodes in rows A and D and the needle electrodes inrows C and B are respectively opposed to each other but deviated inlevel from each other that is, needle electrodes C and D underlie theplane of electrodes A and B in FIG. 3.

FIG. 4 schematically shows the arrangement of the needle electrodes.Cross marks represent needle electrodes D and B and circular marksrepresent underlying needle electrodes C and A.

FIG. 5 shows another arrangement, in which a row of needle electrodes 10is provided on one side of the path of movement of the paper and a rowof needle electrodes 11 is provided on the other side in opposed butstaggered relationship with the row 10. When viewed in the direction ofmovement of the paper, there are rows of needle electrodes 12 and 13,the row of needle electrodes 13 being essentially opposed to the row ofneedle electrodes 12 but directed toward gaps between needle electrodes12. There are further rows of needle electrodes 14 and 15, whichcorrespond to rows of needle electrodes 16 and 17. The needle electrodesin rows 10 to 17 are disposed in such a manner that none of them liesbehind any other adjacent row needle electrode as viewed in thedirection of movement of the paper indicated by 18.

We claim:

1. In corona discharge apparatus having a longitudinal passage formovement therethrough of a chargeable member adapted for use inelectrophotography, an assembly of electrodes each electrode thereincomprising an elongated body tapering to a corona discharge point, saidassembly including first and second longitudinally spaced rows ofelectrodes disposing their discharge points on one side of said passageand third and fourth longitudinally spaced rows of electrodes inrespective facing relation to said first and to said second electroderows and disposing their discharge points on a side of said passageopposite said one side, each of said first row electrode dischargepoints being spaced laterally in said apparatus from each of said thirdrow electrode discharge points, each of said second row electrodedischarge points being spaced laterally in said apparatus from each ofsaid fourth row electrode discharge points.

2. The invention claimed in claim 1 wherein said electrode dischargepoints are uniformly spaced from the electrode discharge points adjacentthereto in the same electrode row.

3. The invention claimed in claim 2 wherein said uniform electrodedischarge point spacing is the same for each said electrode row.

4. in corona discharge apparatus having a longitudinal passage formovement therethrough of a chargeable member adapted for use inelectrophotography, an assembly of electrodes each comprising anelongated body tapering to a corona discharge point, including:

a first plurality of A A A, electrodes, providing a first plurality ofPA PA PA corona discharge points disposed at a first side of saidpassage in a first plane laterally transverse to said passage;

21 second plurality of B B B,, electrodes, providing a second pluralityof P8,, P8 PB, corona discharge points disposed in said first plane at asecond side of said passage opposite said first passage side;

a third plurality of C,, C C,, electrodes, providing a third pluralityof PC PC t PC,, corona discharge points disposed at said first passageside in a second plane longitudinally spaced from said first plane andlaterally transverse to said passage; and

a fourth plurality of D,, D D, electrodes, providing a fourth pluralityof PD PD PD, corona discharge points disposed in said second plane atsaid second passage side,

said first and second plurality corona discharge points being spacedlypositioned in said first plane in the succession PA P13 PA P13 PA, PB,said third and fourth plurality corona discharge points being spacedlypositioned in said second plane in the succession PC PD,, PC PD PC PD 5.The invention claimed in claim 4 wherein said first and third pluralitycorona discharge points are disposed in a third plane transverse to saidfirst and second planes and wherein said second and fourth pluralitycorona discharge points are disposed in a fourth plane transverse tosaid first and second planes.

6. The invention claimed in claim 4 wherein the spacing between coronadischarge points in the succession PA,, P8,, is uniform and wherein thespacing between corona discharge points in the succession PC PD, isuniform.

7. The invention claimed in claim 6 wherein said uniform coronadischarge point spacings are equal. I

8. The invention claimed in claim 7 wherein corona discharge points PAand PD, are both disposed in a common plane longitudinally transverse tosaid passage.

* i IF

1. In corona discharge apparatus having a longitudinal passage formovement therethrough of a chargeable member adapted for use inelectrophotography, an assembly of electrodes each electrode thereincomprising an elongated body tapering to a corona discharge point, saidassembly including first and second longitudinally spaced rows ofelectrodes disposing their discharge points on one side of said passageand third and fourth longitudinally spaced rows of electrodes inrespective facing relation to said first and to said second electroderows and disposing their discharge points on a side of said passageopposite said one side, each of said first row electrode dischargepoints being spaced laterally in said apparatus from each of said thirdrow electrode discharge points, each of said second row electrodedischarge points being spaced laterally in said apparatus from each ofsaid fourth row electrode discharge points.
 2. The invention claimed inclaim 1 wherein said electrode discharge points are uniformly spacedfrom the electrode discharge points adjacent thereto in the sameelectrode row.
 3. The invention claimed in claim 2 wherein said uniformelectrode discharge point spacing is the same for each said electroderow.
 4. In corona discharge apparatus having a longitudinal passage formovement therethrough of a chargeable member adapted for use inelectrophotography, an assembly of electrodes each comprising anelongated body tapering to a corona discharge point, including: a firstplurality of A1, A2, . . . An electrodes, providing a first plurality ofPA1, PA2, . . . PAn corona discharge points disposed at a first side ofsaid passage in a first plane laterally transverse to said passage; asecond plurality of B1, B2, . . . Bn electrodes, providing a secondplurality of PB1, PB2, . . . PBn corona discharge points disposed insaid first plane at a second side of said passage opposite said firstpassage side; a third plurality of C1, C2, . . . Cn electrodes,providing a third plurality of PC1, PC2, . . . PCn corona dischargepoints disposed at said first passage side in a second planelongitudinally spaced from said first plane and laterally transverse tosaid passage; and a fourth plurality of D1, D2, . . . Dn electrodes,providing a fourth plurality of PD1, PD2, . . . PDn corona dischargepoints disposed in said second plane at said second passage side, saidfirst and second plurality corona discharge points being spacedlypositioned in said first plane in the succession PA1, PB1, PA2, PB2, . .. PAn, PBn, said third and fourth plurality corona discharge pointsbeing spacedly positioned in said second plane in the succession PC1,PD1, PC2, PD2, . . . PCn, PDn.
 5. The invention claimed in claim 4wherein said first and third plurality corona discharge points aredisposed in a third plane transverse to said first and second planes andwherein said second and fourth plurality corona discharge points aredisposed in a fourth plane transverse to said first and second planes.6. The invention claimed in claim 4 wherein the spacing between coronadischarge points in the succession PA1, . . . PBn is uniform and whereinthe spacing between corona discharge points in the succession PC1, . . .PDn is uniform.
 7. The invention claimed in claim 6 wherein said uniformcorona discharge point spacings are equal.
 8. The invention claimed inclaim 7 wherein corona discharge points PA1 and PD1 are both disposed ina common plane longitudinally transverse to said passage.